Processing Method For Fiber Material Used To Form Biocomposite Component

ABSTRACT

The present invention is directed to plant fiber-reinforced biocomposite thermoplastic and/or resin compositions and a method for reinforcing thermoplastic resins. The present invention provides a use for the cellulose portion of a plant material, which is the portion left over after processing the selected plant materials to separate the cellulose in a mechanical process that does not damage the internal molecular structure of the cellulose fraction, enabling the cellulose fraction to chemically bond with the thermoplastic resin to enhance the reinforcement of the resin or thermoplastic biocomposite composition.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority as a continuation-in-part of U.S.Non-Provisional patent application Ser. No. 13/648,738, filed on Oct.12, 2012, the entirety of which is expressly incorporated by referenceherein.

FIELD OF THE DISCLOSURE

The present invention relates to a method for obtaining high-strengthfibers of plant materials for use in reinforcing biocompositecompositions. More particularly, the plant fibers are obtained from theraw plant material in a manner that minimizes any alteration of ordamage to the interior molecular structure of the fibers to enhance thestrength of the fibers when utilized to reinforce the biocompositecomposition.

BACKGROUND OF THE DISCLOSURE

The plastics industry is one of the largest consumers of organic andinorganic fillers. Inorganic fillers such as calcium carbonate, talc,mica and the like are well known, as well as organic fillers such aswood flour, chaff and the like, fibrous materials such as asbestos andglass fiber, as well as graphite, cokes, blown asphalt, activatedcarbon, magnesium hydroxide, aluminum hydroxide and the like. All ofthese additives have high specific gravities and their ability toimprove physical properties of the composition is limited.

As an alternative to particulate fillers, thermoplastic materials canalso be formed with fibrous materials to overcome those deficiencies.Fiber-reinforced composite materials based on thermoplastic materialsare being increasingly used in many areas of technology in place ofmetallic materials as they promise a substantial reduction in weight,with mechanical characteristics which are otherwise comparable in manyrespects. For that purpose, besides the thermoplastic matrix, thesecomposite materials include a fibrous component which has a considerableinfluence on mechanical characteristics, in particular tensile andflexural strength as well as impact toughness of the composite material.Fibrous components used are (i) fibers of inorganic materials such asglass, carbon and boron, (ii) metallic fibers, for example of steel,aluminum and tungsten, (iii) synthetic organic fibers, for example ofaromatic polyamides, polyvinyl alcohols, polyesters, polyacrylates andpolyvinyl chloride, or (iv) fibers of natural origin, for example hempand flax.

The use of glass fiber-reinforced thermoplastic materials has ofparticular significance. In FIG. 1, a prior art process for theincorporation of glass fibers into a plastic resin, such aspolypropylene, is illustrated. The polypropylene 10 is initiallycombined at a suitable temperature and pressure with the glass fibers 12and other additives 14, as desired. The polypropylene 10, glass fibers12 and additives 14 are mixed to form the composite material 16. Thiscomposite material 16 can be subsequently extruded at 18 for use in aninjection molding process 20 to form a final molded product 22 havingproperties provided by the combination of the polypropylene 10 and glassfibers 12, along with any additional desired properties provided by theadditives 14.

However, the production of glass fibers requires the use of considerableamounts of energy and the basic materials are not biological in originso that the sustainability of the production process is open tocriticism from ecological points of view. Furthermore, the disposal ofglass fiber-reinforced thermoplastic materials is made difficult as evenupon thermal decomposition of the material, considerable amounts ofresidues are left, which generally can only be taken to a disposal site.Finally glass fibers involve a high level of abrasiveness so thatprocessing the materials in the context of usual processing methods forthermoplastic materials encounters difficulties.

Because of the above-mentioned disadvantages but also generally toimprove the material properties therefore at the present time there isan intensive search for possible ways of replacing the glass fiberswhich dominate in many technical uses, as a reinforcing component.Organic fibrous materials of natural origin, such as plant materialsappear to be particularly attractive in this connection because of theirlower density and the reduction in weight that this entails in thecomposite material as well as sustainability and easier disposal.

The potential of using natural or plant fibers in plastic applicationsas a substitute for synthetic fibers such as glass, carbon, nylon,polyester, etc. has been recognized. For example, Kolla et al. U.S. Pat.No. 6,133,348, which is hereby expressly incorporated by referenceherein, describes flax shives reinforced thermoplastic compositions anda method for reinforcing thermoplastic resins. The invention disclosedin Kolla provides a use for flax shives or particles in thethermoplastic compositions, which is the portion left over afterprocessing plant materials to separate plant fibers (bast fibers) fromthe shives. The shives are the core tissue fibers which remain after thebast fibers are removed from the flax stem via the mechanical separationprocess disclosed in Leduc et al. U.S. Pat. No. 5,906,030, or othermechanical separation processes involving the hammering or bending ofthe natural plant fibers. These core tissue fibers include thecellulose, hemi-cellulose and lignin components of the flax fiber, alongwith a smaller portion of the woody bast fibers that remain on theshives, giving the shives a fiber purity of approximately eightypercent, at maximum.

It will be noted however that the use of natural fibrous materials as afiber-reinforcing component can be confronted with worse mechanicalcharacteristics in the resulting composite materials, in comparison withfiber-reinforced composite materials with glass fiber constituents.Furthermore natural fibers such as flax, hemp or also wood particles areof a fluctuating composition: individual batches of the material differdepending on the respective cultivation area, cultivation period,storage and possibly preliminary treatment. That means however that themechanical characteristics of the fiber-reinforced thermoplasticmaterials to be produced also vary, which makes technical use thereofmore difficult. The material can further change in form and appearanceby virtue of progressing degradation processes. Finally, the constituentcomponents of the various natural fibers can themselves create issueswhen the fibers are utilized in this manner. In particular, thehemi-cellulose fraction of natural fibers absorbs moisture, causing adetrimental effect on the dimensional stability and water resistanceproperties of any thermoplastic material to which the natural fibers areadded.

Furthermore, due to the myriad of environmental and production issuesconcerning the use of plastic materials in general, it is desirable todevelop materials that can provide the same attributes as plasticmaterials, including fiber-reinforced plastic material.

As an alternative to plastics including natural fiber reinforcingmaterials, biocomposite materials are often utilized as a substitute,particularly for low end plastic and fiberglass materials. One of theshortcomings of biocomposite materials is that the fibers includedwithin the biocomposite material only act as a tiller layer and do notform a bond with the other components of the biocomposite, therebyreducing the strength and durability of the biocomposite materials. Aprimary reason for this is that the fibers used to reinforce thebiocomposite material have an interior molecular structure that is oftendamaged as a result of the mechanical processes used for obtaining thefibers form the raw plant material. This damage prevents the fibers fromeffectively bonding with the other biocomposite materials, therebypreventing the biocomposite materials from being fully reinforced by thefibers.

As a result it is desirable to develop a method for obtaining thereinforcing fibers from raw plant material that preserves the interiormolecular structure of the fibers such that the fibers can formeffective bonds with the other biocomposite materials, thereby enhancingthe strength and durability of the biocomposite materials.

SUMMARY OF THE DISCLOSURE

According to one aspect of the present disclosure, fibers of naturalplant materials are used in the filling and reinforcement of formedbiocomposite materials including the fibers. The fibers are obtainedfrom the plant materials in a manner that enables the fibers to besubstituted for the synthetic fibers and form chemical bonds with theother biocomposite material components to at least achieve similarmechanical characteristics for the biocomposite material as whensynthetic fibers are used, in particular the tensile and flexuralstrength as well as impact toughness. In addition the use of the fibersof natural plant materials do not absorb and retain water, and thus donot detrimentally affect the waterproof properties of the biocompositematerial. Further, the fibers of the natural plant component do notcompromise the ability of the biocomposite material to be readilydisposed of and/or recycled.

According to another aspect of the present disclosure, the natural plantfibers are mechanically treated prior to chemical treatment in order toobtain relatively pure plant material for use in the chemical extractionprocess. The particular mechanical treatment or decortication isaccomplished in a manner that reduces the breakage of the core fibers,leaving the interior molecular structure of the fibers undamaged. Thisresults in fibers that after further treatment can chemically bond withthe components of the biocomposite composition to provide a strongerbiocomposite composition with enhanced strength and lighter weight thanother biocomposite materials.

Numerous additional, objects, aspects and advantages of the presentinvention will be made apparent from the following detailed descriptiontaken together with the drawing figures.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawing figures illustrate the best mode of practicing the presentdisclosure.

In the figures:

FIG. 1 is a schematic view of a prior at composite material productionprocess;

FIG. 2 is a schematic view of a first embodiment of a composite materialproduction process according to the present disclosure; and

FIG. 3 is a schematic view of a second embodiment of a compositematerial production process according to the present disclosure.

DETAILED DESCRIPTION OF THE DISCLOSURE

Referring now to the drawing figures in which like reference numeralsdesignate like numerals throughout the disclosure, FIG. 2 illustrates aprocess for the formation of a product 116 created using a compositematerial 102.

The composite material 102 is formed of a thermoplastic resin ormaterial 104, which is the term used to denote polymer materials whichare soft or hard at the temperature of use and which have a flowtransitional range above the temperature of use. Thermoplastic resins ormaterials comprise straight or branched polymers which in principle arecapable of flow in the case of amorphous thermoplastic materials abovethe glass transition temperature (T_(g)) and in the case of (partly)crystalline thermoplastic materials above the melting temperature(T_(m)). They can be processed in the softened condition by pressing,extruding, injection molding or other shaping processes to afford shapedand molded parts. The thermoplastic material 104 used in the presentdisclosure can be any suitable thermoplastic resin material orcombination of multiple thermoplastic materials, such as a plasticincluding one or more natural or petroleum based thermoplastic resinssuch as polyethylene, polypropylene, polystyrene, polyvinyl chloride,polyacryl nitrite, polyamides, polyesters. polyacrylates and Poly LacticAcid (PEA), among others. The thermoplastic material does not have to bea homopolymer but can also be in the form of a copolymer, a polypolymer,a block polymer or a polymer modified in sonic other fashion.Polypropylene is a particularly useful thermoplastic material for use informing the composite material 102 of the present disclosure.

In addition to the thermoplastic material 104, the composite material102 includes cellulose fibers 106. These fibers 106 can be obtained fromany suitable natural plant material 109, such as natural fibrous plantmaterials including a) seed fiber plants, in particular linters, cotton,kapok and poplar down, b) bast fiber plants, in particular sclerenchymafibers, bamboo fibers, (stinging) nettles, hemp, jute, linen or flax(fibre flax and oil seed flax), and ramie, c) hard fiber plants, inparticular sisal, kenaf and manila, coir, and e) grasses. Bast fiberplants, such as flax and hemp, are particularly useful natural nonwoody, plant materials from which the cellulose fibers 106 can beobtained.

The bast plants include outer bast fibers that run longitudinally alongthe length of the plants and core tissue fibers disposed within theouter bast fibers. Because the core tissue fibers are the desiredfibers, the outer bast fibers must be removed prior to use of the corefibers. In removing the outer bast fibers, care must be taken to avoiddamaging or breaking the core tissue fibers in order to maximize thelength of the core tissue fibers. Thus in a first step the straw isratter under controlled environmental conditions (e.g., field rated,chemically rated and/or water rated) followed by mechanically treatingthe bast plant materials, in which the plant materials are decorticatedby shearing the bast fibers from the core tissue fibers, as opposed tohammering or bending/flexing the plant material as in priordecortication processes. By shearing the bast fibers from the coretissue fibers, the core fibers can be kept intact more readily, therebymaintaining the overall strength and length of the core fibers. Usingthis process, core fibers of approximately 95-98% purity can beobtained. In addition, both ratted and non-ratted plant material can beused in the decortications process to obtain a clean core tissue fiberthat can be used for production of the composite material.

In each case, the core fibers of the natural fibrous plant materials 109include cellulose, hemi-cellulose and lignin components. To obtain thecellulose fibers 106 utilized to form the composite material 102 fromthe natural plant material, the hemi-cellulose fraction 108 and ligninfraction 110 are separated from the cellulose fibers or fraction 106,such that a purified crystalline cellulose fraction 106 can be added tothe thermoplastic material 104 to form the composite material 102.

To separate the cellulose fibers/fraction 106 from the hemi-cellulosefraction 108 and lignin fraction 110 of the natural plant material 109,any suitable process 111 can be utilized, such as those employed onnatural plant materials 109 for paper pulping, e.g., soda or kraftpulping, among others. More specific examples of processes for theseparation of the hemi-cellulose fraction 108 and lignin fraction 110from the cellulose fibers 106 of the plant material 109 include thosethat utilize an alkaline material 113, examples of which are disclosedin Hansen et al. U.S. Patent Application Publication No. 2009/0306253and Costard U.S. Patent Application Publication No. 2010/0176354, amongothers, each of which are hereby expressly incorporated by referenceherein in their entirety.

One suitable example is an alkaline separation process shown in CostardU.S. Patent Application Publication No. 2010/0176354 where a naturalplant fiber material 109 is solubilized in an alkaline manner and whichis characterized in that the natural fiber material 109 is treated withan alkaline material 113 without being subjected to mechanical stress a)at a temperature of between 5 and 30° C. and then b) at a temperature ofbetween 80 and 150° C., and is then optionally washed and/or dried.

The alkaline materials 113 that can be used are, among other suitablealkaline materials, alkali metal hydroxide, in particular sodiumhydroxide or potassium hydroxide, alkali metal carbonates, in particularsodium carbonate or potassium carbonate, or alkali metal phosphates, inparticular trisodium phosphate or tripotassium phosphate.

The fiber degradation takes place at a pH of approximately between 8 to14, preferably 10 to 14, more preferably 11 to 12 in the cold process(step a)) and preferably at a temperature of between 10 and 30° C.,preferably between 10 and 25° C., in particular between 15 and 25° C.,more preferably between 15 and 20° C.

The cold treatment according to step a) takes place over a period of 10minutes to 3 hours, in particular 15 minutes to 2 hours and preferably30 minutes to 1 hour. The hot treatment used according to step b) of thenatural fiber material also takes place between a pH of 8 to 14,preferably 10 to 14, more preferably 11 to 12, and preferably at atemperature of between 80 and 140° C., preferably between and 140° C.,in particular between 90 and 135° C., more preferably between 100 and135° C.

The hot treatment according to step b) takes place preferably over aperiod of 20 minutes to 1.5 hours, in particular 30 minutes to 1 hourand preferably 45 minutes to 1 hour. The concentration of alkalinematerial in water in steps a) and/or b) is, based on the activeingredient (typically a solid), preferably in the range from 5 to 15g/l, in particular 7 to 13 g/l, preferably 8 to 12 g/l, particularlypreferably at about 10 g/l.

The process performed according to steps a) and b) effectively dissolvesthe hemi-cellulose fraction 108 and lignin fraction 110 from the naturalplant material 109, which can subsequently be removed with the alkalinesolution, leaving the cellulose fraction 106 behind for subsequentwashing and drying to a desired moisture level, e.g., about 2% by weightor below.

The alkaline treatment according to the disclosure can be supported byadding excipients. Dispersants, complexers, sequestering agents and/orsurfactants are suitable here. Water glass and foam suppressors canlikewise optionally be used depending on the end-application. Othercustomary excipients can also be used. The addition of a complexer,dispersant and/or surfactant to the baths can accelerate and intensifythe wetting of the fibers. The materials customarily used for theserespective purposes in fiber treatment are suitable here.

When separated, the cellulose fibers 106 are at least 95% w/w purecellulose fibers. i.e., the fibers 106 contain not more than about 5weight percent of material other than cellulose, i.e., lignin andhemi-cellulose. Further, the cellulose fibers 106 have a mean fiberlength of less than about 2 mm.

Once liberated from the natural plant material 109, the cellulose fibers106 can be utilized to form the composite material 102. These fibers 106can be colored easily as the fibers 106 are very light, i.e., almostwhite in color and the composite made out of these is odorless. Chemicaltreatment of fiber 106 affects the cellulose structure, e.g., decreasingcrystallinity and increasing the amorphous structure. For example, thechemical treatment opens the bonds in the cellulose fraction or fibers106 for interaction with the polymer matrix 104 in forming thecomposites 102. The composite material 102 of the present disclosure maymixed together and processed by extrusion, compression molding,injection molding, or any other similar, suitable, or conventionalprocessing techniques for synthetic or natural biocomposites.

FIG. 2 shows one embodiment of the processing of the composite material102 of the present disclosure. The ingredients of the composite material102, i.e., a thermoplastic material 104 and the cellulose fibers 106,may be blended or compounded with one another in a manner effective forcompletely blending the cellulose fibers 106 with the thermoplasticmaterial 104, such as in a suitable mixer, e.g., a high or low intensitymixer. Depending upon the particular composition of the thermoplasticmaterial 104 and the cellulose fibers 106, the temperature of the mixerin one embodiment should be from about 140° C. to about 220° C. for theproper combination of the components to form the composite material. Oneexample of a mixer effective for blending the fibers 106 andthermoplastic material 104 is a high intensity thermokinetic mixer. Inthese types of mixers, frictional energy heats the contents until theybecome molten, a process that takes seconds or minutes depending on thespeed of the impeller. In another aspect of the invention, heat from anexternal source can be supplied to melt the thermoplastic material 104and effect blending of the cellulose fibers 106. An example of a lowintensity mixer is a ribbon blender.

The formulation of the composite material 102 can be tailored bymodifying the amounts or ratios of the thermoplastic material 104 andthe cellulose fibers 106 used to form the composite material 102depending on the particular application and/or function for thecomposite material 102. Additives (including, but not limited to, flowenhancers, anti-oxidants, plasticizers. UV-stabilizers, foaming agents,flame retardants, etc.) are used in formulation to enhance thefunctionality of the composite product. To accommodate the particularuse and corresponding required properties of the composite material 102,the blending of the polymers/thermoplastic material 104 and the fibers106 can also be varied in temperature and pressure. In addition, theblending parameters and component ratios for the composite material 102can be altered depending upon the particular pant material from whichthe fibers 106 are obtained. Examples of the polymers used as thematerial 104 include, but are not limited to acrylonitrile butadienestyrene, polyethylene, polypropylene, polystyrene, polyvinyl chloride,polyacryl nitrite, polyamides, polyesters, polyacrylates, otherengineering plastics and mixtures thereof.

In some particular embodiments of the composite material 102, the weightratios/percentages of the thermoplastic material 104 and the cellulosefibers 106 used in the formation of the composite material 102 rangefrom 1-60%. The fibre loading in biocomposite for the following processcan be varied from process to process. Exemplary fiber loadingpercentages according to various molding processes in which thebiocomposite material 102 is used are as follows:

Extrusion products: 1-30% (product examples: pipes, profiles)

Injection molding: 1-45% (product examples: small to large componentsfor various industries such as agricultural machinery products,automotive interior and under hood products etc.).

Compression molding: 1-60% (product examples: kitchen cabinets, bicyclecomponents, interior products for agricultural machineries (such ascombine, tractor, and automotive (car, bus etc.).

Rotational molding: 1-30% (product examples: water tanks, large storageboxes)

Vacuuming forming/Thermoforming: 1-20% (product examples: packagingmaterials, cups, plates, boxes, building insulation)

In one particular embodiment, the mixing/extruding of the thermoplasticmaterial 104 and the cellulose fiber 106 to form the composite material102 is performed with a dry blender, mixer, parallel screw extruder. Theparallel screws in the device serve to blend the fibers 106homogeneously with the polymer 104, while also reducing the damageand/or breakage of the cellulose fibers 106 in the mixture forming thecomposite material 102. In addition, the parallel screws help to reducethe residence time of the composite material formulation 102 byincreasing the speed of mixing of the components of the compositematerial 102 in the device.

As a result of the use of purified cellulose fibers 106 obtained via themechanical and chemical processing described previously, the fibers 106develop a molecular bonding with the thermoplastic material 104 whenblended to form the composite material 102 which provides superiorperformance of to composite materials having, only mechanical bindingbetween the polymer and the reinforcing fibers. Without wishing to bebound by any particular theory, it is believed that this molecularbonding occurs as a result of the thermoplastic material 104 flowinginto and filling the inside the modified fibers 106 during themixing/extrusion process. The increase in the melting temperature of thebiocomposite 102 indicates a possible polymerization effect of the fiberthat diffuses or dissolves into the polymer in the composite andcorrespondingly increases the thermal resistance of composite. Due tothe porous surface of the treated fiber, molten polymer matrix enters into the porous fiber and interlocks with each other and to form a strongbinding within the biocomposite 102. Further investigation is requiredto determine the exact nature of bond. In addition, polymer matrixesencapsulate the fibre and enhance the biocomposite strength and reducethe porosity and the formation of air pockets within the biocomposite.This molecular bonding between the fibers 106 and the thermoplasticmaterial 104 significantly improves the properties of the compositematerial 102, e.g., mechanical properties including tensile and flexuralstrength as well as impact toughness, and thermal properties. Theproperties of the biocomposite 102 vary as a result of the fibre loadingand the type of polymer and/or additives used in the formation of thebiocomposite 102. This, in turn, enhances the functionality of products122 formed of the composite material 102 and enable the products 122 tobe used in a wider range of industrial applications than priorfiber-reinforced materials. Also, in conjunction with the reduction inprocessing time in the parallel screw device, the molecular bondingbetween the fibers 106 and the polymer 104 limits any significantreduction of inbuilt additives present in polymer/thermoplastic material104. As a result, it is only necessary to supplement any requiredadditives, such as bonding additives, present in the polymer 104 duringthe formulation of the composite material 102, as opposed to adding theentire amount of the additives outside of those contained in the polymer104.

Once mixed/compounded, the melted composite material 102 can be allowedto cool to room temperature and then further processed by conventionalplastic processing technologies. Typically, the cooled blend isgranulated into fine particles. The fine particles are then utilized forextrusion 112, injection 114 and/or compression molding to form finishedparts or products 116.

In an alternative embodiment, the mixer can be operated without heat,such that the thermoplastic material 104 and cellulose fibers 106, afterbeing mixed together, are transferred to a feed hopper, such as agravity feed hopper or a hopper with a control feed mechanism.Alternatively, the thermoplastic material 104 and the cellulose fibers106 can be individually fed to the extruder without being previouslymixed together. The feed hopper transfers the composite to a heatedextruder 112.

The extruder 112 blends the ingredients under sufficient heat andpressure. Several well-known extruders may be used in the presentinvention, e.g., a twin screw extruder. The extruder 112 forces orinjects the composite material 102 into a mold 114. In an exemplaryembodiment, the flow rate of the extruder 112 may be between about 150and 600 pounds per hour. In other embodiments, the flow rate may behigher or lower depending on the type and size of the extruder 112. Theinjection mold 114 may be made up of one or more plates that allow thecomposite material 102 to bond and form a shaped-homogeneous product116. A typical plate may be made from hardened steel material, stainlesssteel material or other types of metals. A cooling system (e.g., aliquid bath or spray, an air cooling system, or a cryogenic coolingsystem) may follow the injection mold 114.

In the mixer, a number of optional processing aids or additives 115 canbe added to the thermoplastic material 104 and the cellulose fibers 106.These processing aids or modifiers act to improve the dispersion offibers 106 in the thermoplastic polymer material 104 and also helpfurther prevent the absorption of water into the fibers 106 and improvethe various thermal, mechanical and electrical properties of thecomposite material 102, e.g., the strength of the resulting compositematerial 102. The addition levels of the modifiers or compatibilizersused depends on the target properties. For example, where higher tensileand flexural strengths are desired, higher levels of modifier orcompatibilizer will be required. A compatibilizer is not required toachieve higher stiffness.

In one particular example of the present disclosure, the compositematerial 102 includes an amount of an wear additive 115 selected fromaluminum or copper powder, or combinations thereof to increase the wearproperties and enhance the longevity of the final product 122.

With regard to the molding processes 120 used to form the final product122, the composite material 102 improves the product 122 formed by theseprocesses 120 through the reduction of the formation of pin holes andthe porosity of the material product 122. Without wishing to be bound byany particular theory, it is believed that these results are achieved inthe composite material 102 as a result of the close packing andincreased density of the fibers 106, polymer 104 and additives 115 dueto the properties of the cellulose fibers 106, and the consequentremoval of entrapped air bubbles during the processing of the fibers 106and thermoplastic material 104, along with the additives 115, to formthe composite material 102. As a result the final product 122 is moresolid and stronger than products formed from prior fiber-reinforcedmaterials.

Further, with the use of the cellulose fibers 106 formed in theabove-described manner, it is possible to achieve higher gradeproperties (mechanical, thermal, electrical, etc.) for the final product122 while using lower grade thermoplastic materials 104 in combinationwith the cellulose fibers 106. In particular, as a result of theproperties and purity of the cellulose fibers 106, the fibers 106 canbond well with a wide range of grade of polymeric/thermoplasticmaterials 104 to achieve products 122 with the desired properties.Further, to address any issues presented by the particularpolymer/thermoplastic material 104, the weight percentage or weightratio of the fibers 106 can be increased, in formulation of compositematerial 104 without compromising the quality and desired properties ofthe final product 122. In addition, by increasing the amount of thecellulose fibers 106 utilized in the composite material 102, theconsequent consumption of the polymer 104 will be reduced.

For a better understanding of the objects and advantages of the presentinvention, the same will be now described by means of several examples.However, it should be understood that the invention is not limited tosuch specific examples, but other alterations may be contemplated withinthe scope and without departing from the spirit of the invention as setforth in the appended claims.

While the formulation of the particular biocomposite material 102depends on the final product 122 formed from the biocomposite material102, its functionality, and/or as described above the particular moldingprocess used to form the biocomposite material 102 into the finalproduct 122.

In one example of biocomposite composition 102, the formulationincludes:

a) natural/petroleum based thermoplastic material(s): 99-40% w/w

b) fiber 1-60% w/w

c) additives 1-5% w/w.

Biocomposite materials 102 of different grade (e.g., extrusion grade,injection grade, compression grade, rotational grade, vacuum forminggrade) are manufactured by changing the formulation of the biocompositematerial 102, and in one example by changing the amount of fiber 106present and consequently adjusting the percentages of the remainingcomponents.

One particular example of a thermoforming/vacuum forming formulation forthe biocomposite material 102 is as follows:

a) polystyrene

b) treated natural fiber

c) butane

d) additives (zinc stearate, magnesium stearate)

e) talcum powder.

Other examples of biocomposite material 102 formed according to thepresent disclosure are found in the following tables. The properties canbe modified according to product requirement by changing/modifying theformulation

TABLE 1 Properties Liner low density polyethylene - dicumyl peroxidepre-treated flax fibre Flax straw/Industrial Hemp stalk ChemicallyComposite Unretted Field retted Water retted retted properties Unit FlaxHemp Flax Hemp Flax Hemp Flax Hemp Melt Flow g/10 min 2.8 2.6 3.7 3.54.1 3.4 3.8 3.5 Index Melting point ° C. 130 128 129 127.4 130.1 128130.6 129 1 Tensile Mpa 13.2 15.3 17.6 16.9 18.3 18.7 22.2 21 StrengthTensile Impact KJ/m² 178 172 188 182 194 178 223 205 strength HardnessSD 12 11 17 18 18 17 23 21 Water % 3-5 2-6 <1 <1 <1 <1 <1 <1absorption@50 RH

TABLE 2 Properties Liner low density polyethylene - triethoxyvinylsilanepre-treated flax fibre Flax straw/Hemp stalk Chemically CompositeUnretted Field retted Water retted retted properties Unit Flax Hemp FlaxHemp Flax Hemp Flax Hemp Melt Flow g/10 min 2.0 2.2 2.7 2.4 2.6 2.4 2.82.4 Index Melting point ° C. 129 131.2 128.6 129 129 129 129 129.6Tensile Mpa 15 14.2 18.4 17.1 20.1 17.4 19.3 17.9 Strength at YieldTensile Impact KJ/m² 178 161 188 186 199 193 218 209 strength HardnessSD 9 11 14 15 19 19 20 18 Water % 3-5 2-6 <1 <1 <1 <1 <1 <1absorption@50 RH

TABLE 3 Properties High density polyethylene - benzoyl chloridepre-treated flax fibre Flax straw/Hemp stalk Chemically CompositeUnretted Field retted Water retted retted properties Unit Flax Hemp FlaxHemp Flax Hemp Flax Hemp Melt Flow g/10 min 1 1.2 1.6 1.5 1.8 1.7 1.81.4 Index Melting point ° C. 130 128 130 130 129 130 129 130 Tensile Mpa16.3 13.7 16.3 16.2 18 18.1 23.4 19.2 Strength at Yield Tensile ImpactKJ/m² 167 157 177 179 188 185 221 178 strength Hardness SD 17 11 12 1519 22 21 19 Water % 3 2 <1 <1 <1 <1 <1 <1 absorption @50 RH

TABLE 4 Properties High density polyethyene - dicumyl peroxidepre-treated flax fibre Flax straw/Hemp stalk Chemically CompositeUnretted Field retted Water retted retted properties Unit Flax Hemp FlaxHemp Flax Hemp Flax Hemp Melt Flow g/10 min 0.5 0.8 1.0 1.5 1.2 1.6 1.61.5 Index Melting point ° C. 130 126 131.6 128.4 128 129 129 128 TensileStrength Mpa 15 14.3 16.8 15.4 17.5 18.1 24.1 21.2 at Yield TensileImpact KJ/m² 180 167 197 180 185 185 220 180 strength Hardness SD 13 914 12 15 12 17 15 Water % 3 2 <1 <1 <1 <1 <1 <1 absorption@50 RH

Oilseed flax and industrial hemp fiber has promising future in theplastic industries. It is observed that unretted and chemically rettedflax and hemp can be used in plastic composite (LLDPE and HDPE).Chemically retted fiber increased the T_(m) of composite compared topure polyethylene. The increase of T_(m) may be attributed to thepolymerization effect of the fiber that diffuses or dissolves into thepolymer in composite and increased the thermal resistance of composite.This investigation indicated that chemical retting has a great influenceon mechanical properties of (flax and hemp) polymer composites productsdeveloped through rotational molding processes.

Looking now at FIG. 3, a second embodiment of the process for formingthe biocomposite material 102 formed with a thermoplastic material 104is shown according to the present disclosure.

Similar to the first embodiment in FIG. 2, in addition to thethermoplastic material 104, the biocomposite material 102 includes plantmaterial fibers 108. These Fibers 108 can be obtained from any suitablenatural plant material 106, such as natural fibrous plant materialsincluding a) seed fiber plants, in particular linters, cotton, kapok andpoplar down, b) bast fiber plants, in particular sclerenchyma fibers,bamboo fibers, (stinging) nettles, hemp, jute, linen or flax (fibre flaxand oil seed flax), and ramie, c) hard fiber plants, in particularsisal, kenaf and manila, d) coir, and e) grasses. Bast fiber plants,such as hemp and oil seed flax, are particularly useful naturalnon-woody, plant materials from which the fibers 108 can be obtained.

The bast plants include outer bast fibers that run longitudinally alongthe length of the plants and core tissue fibers disposed within theouter bast fibers. Because the core tissue fibers are the desiredfibers, the outer bast fibers must be removed prior to use of the corefibers. In removing the outer bast fibers, care must be taken to avoiddamaging or breaking the core tissue fibers in order to prevent damagefrom being done to the interior molecular structure of the core fibers,as well as to maximize the length of the core tissue fibers. Thus in afirst step 210 the plant material or straw 106 is ratted in a storagelocation for the straw or other desired plant material under controlledenvironmental conditions (e.g., field ratted, dew ratted, chemicallyratted and/or water rated). Additionally, in an alternative embodiment,the oil seed flax or other plant material 106 can be utilized withoutstep 110, such that the material is unratted.

After step 210, the plant material 106 is cleaned in step 212. To cleanthe plant material 106, initially the material is semi-broken in step214 by using a roller breaker at low rpm with little or no stressapplied to the plant material 106. Subsequently the plant material isair and gravity cleaned in step 216 by placing the plant material in asuitable tumbling machine (uniaxial biaxial/multiaxial/rock and roll)with a fixed low rpm and directing a high speed air flow past and aroundthe plant material as is it tumbled in the machine. This actionseparates any loosely attached sieve and dust from the plant material106. After tumbling, in step 218 the plant material 106 is cleaned in asuitable cleaning device to remove the remaining sieve and dust from theplant material 106. If the straw is too dirty, e.g., mud is attached toit, then it can be washed in water in between 22 to 50° C. and dried forfurther mechanical processing.

Once the straw or plant material 106 has been cleaned, in step 220 thebast plant materials are mechanically treated, in which the plantmaterials are decorticated to remove the bast fibers from the coretissue fibers 108, as opposed to hammering or bending/flexing the plantmaterial as in prior art decortication processes. By decorticating thebast fibers from the core tissue fibers 108, the core fibers 108 canmore readily be kept intact, thereby maintaining the overall interiormolecular structure and corresponding strength intact, and maintainingan increased length of the core fibers 108. Various processes fordecortication can be used, so long as the process places little or nostress on the core fibers 108 so that the interior molecular structureremains undamaged, unlike other prior art processes that involvehammering or bending the plant material to remove the bast fibers. Someexamples of deeortication processes that can be used in step 220 includetumbling, scutching, picking and grading the plant materials 106. Usingthese processes, core fibers of approximately 95-98% purity can beobtained. In addition, both ratted and non-ratted plant material 106 canbe used in the decortications process to obtain a clean, core tissuefiber 108 that can be used for production of the composite material.

Once removed from the bast fibers, the crude core fibers 108 are passedthrough at least one or more, and in one embodiment, a series of five(5) machines to produce the fine, clean and uniform core fibers 108 foruse as biocomposite reinforcement fibers. First, the crude core fibers108 are moved in step 222 to a combing machine in order to eliminate anyremaining shive and to align the fibers into a clean fiber bundle.

In step 224, the bundles of the clean, crude core fibers 108 are passedthrough a micro-combing process which serves to open the crude fibersand separate the individual core fibers 108 in the bundle from oneanother. In performing this individual fiber separation, the aspectratio of the individual fibers 108 is increased to enhance thereinforcement effect of the fibers 108 in the biocomposite. In this step224, or as a modification to step 224, the fibers 108 can have anantistatic lube applied thereto to enhance the separation of the fibers108.

In step 226, once separated the individual fibers 108 can be processedthrough a carder to align the finer premium quality fibers (clean, long,align, more uniform, strong) while discarding the lower quality fibers.The high quality fibers 108 are then combined in a suitable device intoa roving, or a rope-like alignment of the fiber matrix in step 228,which is subsequently dried, by using drier such as in a dehumidifier, athin layer drier cabinet, an oven or an RF or microwave drier, amongother suitable devices to keep it dried. Drying conditions depend uponthe particular device and the drying requirement (0-6% water w/w or v/v)and RH in step 230.

In step 232, the roving from step 230 is chopped or sheared into thedesired size having the highest aspect ratio (i.e., length to diameter,for example 2 mm fiber for short biocomposite) for optimum reinforcementof the biocomposite material 102. The chopped roving can then be addedin step 234 to the thermoplastic material 104 in either a pre-mixedstate or directly into the hopper of an extrusion or injection moldingmachine to form the reinforced biocomposite material 102. Thecombination or mixing of the roving with the thermoplastic material 104in step 234 can be accomplished by spraying the chopped fiber material108 into the thermoplastic material 104, or by any of the manners andprocesses described previously with regard to the embodiment of FIG. 2with any of the disclosed additives, processing aids disclosed withregard to the embodiment of FIG. 2.

Two ways fiber can be processed. One without chemical treatment andother chemically treated, in both cases same mechanically fiberprocessing steps need to be followed. Prior to either the combing step222 or the micro-combing step 224, the core fibers 108 of the naturalfibrous plant materials 106 can be chemically treated as illustrated instep 225 in order to separate the cellulose fibers 108 from thehemi-cellulose and lignin components of the core fibers or crude fibercan be processed and later it can go for chemical treatment prior todevelop biocomposite formulation. The process employed in step 225 issimilar to that used in step 111 of the embodiment of FIG. 2, such thata purified crystalline cellulose fraction of fibers 108 having an intactinternal molecular structure can be added to the thermoplastic material104 to form the composite material 102.

Once liberated from the natural plant material 106 in step 225, thecellulose fibers 108 can be further processed in either themicro-combing step 224 or both the combing step 224 and micro-combingstep 226 to form fibers 108 having the desired attributes for additionto the thermoplastic material 104 to form the biocomposite 102 asdescribed above.

Various other alternatives are contemplated is being within the scope ofthe following claims particularly pointing out and distinctly claimingthe subject matter regarded as the invention.

We claim:
 1. A reinforced thermoplastic resin composition comprising: a.a thermoplastic resin; and b. from about 1 to about 60 weight percentcellulose fibers based on the weight of the composition, the cellulosefibers obtained by the decortications of a natural plant material thatdoes not damage the internal molecular structure of the cellulosefibers.
 2. The composition of claim 1 wherein the natural plant materialis selected form the group consisting of natural fibrous plant materialsincluding a) seed fiber plants, in particular linters, cotton, kapok andpoplar down, b) bast fiber plants, in particular sclerenchyma fiberplants, bamboo fiber plants, (stinging) nettles, hemp, jute, linen orflax, and ramie, c) hard fiber plants, in particular sisal, kenaf andmanila, d) coir, and e) grasses.
 3. The composition of claim 1 whereinthe natural plant material is a bast fiber plant material.
 4. Thecomposition of claim 3 wherein the bast fiber plant material is selectedfrom the group consisting of hemp and flax.
 5. The composition of claim3 wherein the cellulose fibers are formed of at least 95% pure cellulosefibers.
 6. The composition of claim 1 wherein the thermoplastic resin isselected from the group consisting of polyethylene, polypropylene,polystyrene, polyvinyl chloride, polyacryl nitrite, polyamides,polyesters, polyacrylates and mixtures thereof.
 7. The composition ofclaim 1 wherein the cellulose fibers and the thermoplastic resin aremolecularly bonded to one another.
 8. A method for reinforcing athermoplastic resin composition comprising: a) providing an amount ofcellulose fibers obtained by the separation of the cellulose fiberfraction from a natural plant material in a decortications process thatleaves the internal molecular structure of the cellulose fiber fractionintact and aligned; and b) blending from about 1 to about 60 weightpercent of the cellulose fibers based on the weight of the compositionwith a thermoplastic resin.
 9. The method of claim 8 wherein the naturalplant material is selected form the group consisting of bast fiberplants.
 10. The method of claim 8 further comprising the step ofseparating the fibers after providing the fibers.
 11. The method ofclaim 8 wherein the step of separating the fibers comprises: a) combingthe fibers; b) micro-combing the fibers; and c) carding the fibers. 12.The method of claim 11 further comprising the steps of: a) forming thefibers after carding into a roving; and b) chopping the roving to adesired length.
 13. The method of claim 8 wherein the step of providingthe cellulose fibers comprises mechanically separating core tissuefibers from outer plant fibers while placing minimal stress on the coretissue fibers.
 14. The method of claim 8 wherein, the step of blendingthe cellulose fibers with the thermoplastic resin comprises mixing thecellulose fibers and the thermoplastic resin in parallel screw mixingdevice to minimize breakage of the interior molecular structure of thecellulose fibers and the residence time of the fibers and resin in themixing device.
 15. The method of claim 8 wherein the step of blendingthe cellulose fibers with the thermoplastic resin comprises formingmolecular bonds between the cellulose fibers and the thermoplasticresin.
 16. A reinforced thermoplastic resin composition comprising: a) athermoplastic material; and b) from about 1 to about 60 weight percentcellulose fibers based on the weight of the composition, the cellulosefibers obtained by the separation of a cellulose fiber fraction fromflax without damaging the internal molecular structure of the cellulosefiber fraction.
 17. The composition of claim 16 wherein the cellulosefibers and the thermoplastic are molecularly bonded to one another. 18.The composition of claim 16 wherein the thermoplastic is a polyolefin orpolyamide or an engineering plastic.
 19. The composition of claim 18wherein the thermoplastic is polypropylene or acrylonitrile butadienestyrene.